JP2019045558A - Heating member, fixation device, and image formation device - Google Patents

Abstract

To provide a heating member, a fixation device, and an image formation device that can reliably block an electric conduction route when a crack occurs.SOLUTION: A heater 23 includes: an insulating substrate 27; a heating resistor 26 provided on the surface of the substrate 27; electrodes 29b and 30b provided on the heating resistor 26 on one end side and the other end side in a shorter direction of the substrate 27 along the longer direction of the substrate 27; conduction sections 29c and 30c disposed on the back surface of the substrate 27, disposed straddling installation regions of the electrodes 29b, 30b and heating resistor 26 in the shorter direction and longer direction, and connected to the electrodes 29b, 30b; and power supplying sections 29a and 30a for supplying power to the electrodes 29b, 30b via the conduction sections 29c, 30c.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a heat generating member for heating a recording material, a fixing device provided with the heat generating member, and an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer provided with the fixing device.

  Conventionally, as a fixing device mounted on an electrophotographic copying machine or printer, a heater as a heat generating member, a flexible member moving while being in contact with the heater, and a heater and a nip portion via the flexible member A pressure roller to form a pressure roller. Such a heater has a heating resistor on a ceramic substrate. The recording material carrying the unfixed image is heated by the heater while being nipped and conveyed by the nip portion, whereby the unfixed image is heated and fixed. Such a fixing device has an advantage that the time required to raise the temperature to the fixable temperature is short after the start of energization of the heater, and that the power consumption in the standby state for waiting for the print command is small.

  In the fixing device of the above configuration, when the recording material of small size is continuously passed, the temperature of the sheet passing area is lowered because the heat is absorbed by the recording material, but the temperature of the non-sheet passing area where it is not passed is the heat To raise the temperature not to be robbed. In the fixing device, when such temperature rise occurs, an image defect such as damage to parts such as a pressure roller or high temperature offset occurs.

  In recent years, in order to solve these problems, a fixing device provided with a heat generating member that suppresses the temperature rise in the non-sheet passing area has been proposed. The heat generating member includes an elongated substrate, an electrode provided along the longitudinal direction of the substrate on one end side and the other end side in the short direction orthogonal to the longitudinal direction of the substrate, and an end on the same side in the longitudinal direction of the substrate It has a power supply unit provided, and a heating resistor electrically connected between the electrodes. The heat generating resistor generates heat by being supplied with electricity from the power supply unit through the electrodes, and has a positive resistance temperature characteristic in which the resistance value increases when the temperature rises. As a result, the resistance value of the non-sheet-passing area of the small size recording material whose temperature rises rises as the temperature rises, so the heat generation is suppressed and the temperature rise is suppressed.

  Here, the heater may cause a crack in the substrate due to thermal stress or mechanical stress at the time of abnormal temperature rise. Such a heater can be considered to have an infinite number of energization circuits in the short direction, so even if a crack occurs in part of the short direction, the conduction circuit is secured and heat generation is continued. Specifically, in the conventional heater, when a crack is generated in the short direction at a position away from the power supply side, since the conduction circuit is secured on the side close to the power supply side, heat generation is continued.

  On the other hand, Patent Document 1 discloses a heating body in which a temperature detection type safety element is installed at one end provided with an electrode in the longitudinal direction of the heating resistor. In the heating element of Patent Document 1, when the operating temperature of the safety element is reached due to the temperature rise, the safety element can operate to interrupt the energization of the heater.

JP, 2008-192398, A

  However, according to Patent Document 1, even if the heater is broken, the safety element does not operate unless the operating temperature of the safety element is reached, and the heater can not be de-energized. For example, in the heater of Patent Document 1, when a crack in the lateral direction is generated at a position away from the power supply side, the conduction circuit is secured on the side close to the power supply side including the contact position of the thermistor 25b. Thus, in the heater of Patent Document 1, when a crack in the lateral direction occurs at a position away from the power supply side, the safety element does not operate because the operating temperature of the safety element is not reached, and the thermistor 25b is used. Temperature control is performed as usual, and heat generation is continued.

  An object of the present invention is to provide a heat generating member, a fixing device and an image forming apparatus capable of reliably interrupting a current path when a crack occurs.

  In the heat generating member according to the present invention, the insulating substrate, the heat generating resistor provided on one surface of the substrate, and the one end side and the other end side of the substrate along the longitudinal direction of the substrate An electrode provided on a heat generating resistor and a back surface of the one surface of the substrate are provided, and are provided across the installation region of the electrode and the heat generating resistor in the lateral direction and the longitudinal direction, It has a conductive part connected to the electrode, and a feed part which supplies electric power to the electrode via the conductive part.

  According to the present invention, it is possible to provide a heat generating member, a fixing device, and an image forming apparatus capable of reliably interrupting the current path when a crack occurs.

FIG. 1 is a schematic view of an image forming apparatus according to Embodiment 1 of the present invention. FIG. 1 is a schematic view of a fixing device according to Embodiment 1 of the present invention. It is A-A 'sectional drawing of FIG. It is a top view of the heater concerning Embodiment 1 of the present invention. It is a bottom view of the heater concerning Embodiment 1 of the present invention. It is a B-B 'sectional view of FIG. It is a top view of the heater concerning Embodiment 2 of the present invention. It is a bottom view of the heater concerning Embodiment 2 of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1
<Configuration of Image Forming Apparatus>
The configuration of the image forming apparatus 100 according to the first embodiment of the present invention will be described in detail with reference to FIG.

  The image forming apparatus 100 includes a photosensitive drum 1, a charging roller 2, a laser beam scanner 3, a developing unit 4, a feeding cassette 5, a feeding roller 6, a registration roller 7, and a transfer roller 9. Have. The image forming apparatus 100 further includes a cleaning unit 10, a fixing device 11, and a discharge tray 14. Here, the image forming apparatus 100 exemplifies a laser printer using a transfer type electrophotographic process.

  The photosensitive drum 1, the charging roller 2, the laser beam scanner 3, the developing unit 4, and the transfer roller 9 constitute an image carrying unit as an image carrying unit for carrying an image on the recording material P.

  The photosensitive drum 1 is a rotating drum type electrophotographic photosensitive member, and rotates at a predetermined speed in the circumferential direction. The photosensitive drum 1 is configured by providing a photosensitive material such as an OPC or an amorphous silicon drum on a cylindrical substrate such as aluminum or nickel.

  The charging roller 2 uniformly charges the surface of the photosensitive drum 1 by rotating in contact with the photosensitive drum 1.

  The laser beam scanner 3 scans and exposes the photosensitive drum 1 whose surface is uniformly charged by the laser light L modulated corresponding to the image information transmitted from an image reading device (not shown) or the like. An electrostatic latent image corresponding to image information is formed on the surface of the photosensitive drum 1.

  The developing unit 4 supplies toner (developer) to the electrostatic latent image formed on the photosensitive drum 1 to develop the electrostatic latent image, and forms a toner image on the photosensitive drum 1.

  The feeding cassette 5 stores the recording material P in a stacked manner.

  The feeding roller 6 separates the recording materials P stored in the feeding cassette 5 one by one and feeds the recording material P to the registration roller 7.

  The recording material is fed by the feeding roller 6 while the registration roller 7 is synchronized such that the timing of entering the transfer nip T between the tip of the toner image on the photosensitive drum 1 and the tip of the recording material P becomes the same. P is introduced into the transfer nip T through the sheet path 8a.

  The transfer roller 9 forms a transfer nip T with the photosensitive drum 1. The transfer roller 9 nips and conveys the recording material P introduced from the registration roller 7 at the transfer nip T. The transfer roller 9 causes the toner image of the photosensitive drum 1 to be transferred onto the recording material P by electrostatic characteristics at the transfer nip T when a transfer bias having a polarity opposite to the polarity of the toner is applied from a transfer bias application power supply (not shown). . The transfer roller 9 separates the recording material P on which the toner image is transferred at the transfer nip T from the surface of the photosensitive drum 1 and conveys the recording material P toward the fixing device 11 through the sheet path 8 b.

  The cleaning unit 10 removes the toner or paper powder on the surface of the photosensitive drum 1 after transferring the toner image to clean the surface of the photosensitive drum 1, thereby making the photosensitive drum 1 repeatedly usable for image formation.

  The fixing device 11 permanently fixes the toner image on the recording material P by heating and pressing the recording material P to which the toner image conveyed from the transfer nip T has been transferred. The fixing device 11 conveys the recording material P, on which the toner image is permanently fixed, toward the discharge port 13 via the sheet path 8 c and discharges the recording material P from the discharge port 13 to the discharge tray 14. The fixing device 11 includes a heater 23 described later.

<Configuration of Fixing Device>
The configuration of the fixing device 11 according to the first embodiment of the present invention will be described in detail with reference to FIG.

  The fixing device 11 includes a stay 21, a fixing film 22, a heater 23, and a pressure roller 24.

  The stay 21, the fixing film 22, the heater 23, and the pressure roller 24 are all elongated members in the longitudinal direction. Here, the longitudinal direction is a direction orthogonal to the conveyance direction of the recording material P.

  The stay 21 is a guide member, and is formed in a vertical cross-section wedge shape using a predetermined material having heat resistance and rigidity.

  The fixing film 22 as a heating and rotating unit is a flexible member and has heat resistance, and is formed in a cylindrical shape. The fixing film 22 is externally fitted to the stay 21. The fixing film 22 has an inner circumferential length larger than the outer circumferential length of the stay 21 by a predetermined length, and is externally fitted to the stay 21 with a margin. The predetermined length is exemplified here as 3 mm.

  A lubricant (not shown) is provided between the inner circumferential surface of the fixing film 22 and the outer circumferential surface of the stay 21 in order to reduce the sliding resistance when the stay 21 and the inner circumferential surface of the fixing film 22 contact and rotate. It intervenes.

  The heater 23 as a heat generating member is held by the stay 21 and is included in the fixing film 22. The heater 23 includes an overcoat layer 28, and the overcoat layer 28 is in contact with the inner peripheral surface of the fixing film 22. The details of the configuration of the heater 23 will be described later.

  The pressure roller 24 as a pressure rotation means includes a core 24a, an elastic layer 24b provided around the core 24a, and an outermost release layer 24c provided around the elastic layer 24b. And. Both ends of the pressure roller 24 in the longitudinal direction of the cored bar 24 a are rotatably held by side plates (not shown) of the fixing device 11. The pressure roller 24 has a predetermined width across the fixing film 22 with the heater 23 by pressing both ends in the longitudinal direction of the cored bar 24 a to the stay 21 side by pressing means such as a pressure spring. The fixing nip N is formed.

<Structure of heater>
The configuration of the heater 23 according to the first embodiment of the present invention will be described in detail with reference to FIGS. 3 to 6.

  The heater 23 includes a thermistor 25a, a thermistor 25b, a heating resistor 26, a substrate 27, an overcoat layer 28, a feeding portion 29a, an electrode 29b, a conductive portion 29c, a feeding portion 30a, an electrode 30b and , And a conductive portion 30c. The heater 23 includes a thermo switch 31, a control unit 41, a triac 42, an AC power supply 43, a current detector 44, a switch 45, a power feeding unit 129a, a conductive unit 129b, and a power feeding unit 129c. have.

  The region surrounded by the length x and the length y shown in FIG. 4 is projected on the back surface of the substrate 27 when the heating resistor 26, the electrode 29b and the electrode 30b provided on the front surface of the substrate 27 are projected on the back surface. It is an installation area including the heating resistor 26, the electrode 29b, and the electrode 30b.

  The thermistor 25 a and the thermistor 25 b are provided in contact with the back surface of the substrate 27 opposite to the surface on the fixing nip N side, and detect the temperature of the heater 23. The thermistor 25 a and the thermistor 25 b output the detection result of the temperature of the heater 23 to the control unit 41. The thermistor 25 a and the thermistor 25 b here provide a heat insulating layer on a support, fix the element of the chip thermistor on this heat insulating layer, press the element against the back surface of the substrate 27 with a predetermined pressure and support Will be illustrated as being in contact with the back surface of the substrate 27.

  The thermistor 25 a is provided in a sheet passing area of the recording material P of the minimum size through which the recording material P always passes in the longitudinal direction of the heating resistor 26. The thermistor 25a detects the temperature of the sheet passing area.

  The thermistor 25 b is provided in a non-sheet passing area when the recording material P of a predetermined small size larger than the minimum size in the longitudinal direction of the heating resistor 26 is passed in the A direction of FIG. 2. The thermistor 25 b detects the temperature of the non-sheet passing area when passing the small size recording material P. The predetermined small size here exemplifies the B5 size.

  The heat generating resistor 26 is provided on the surface as one surface of the substrate 27.

  The substrate 27 is fixed in the groove of the stay 21 so that the surface thereof faces the fixing nip N. The substrate 27 has an elongated shape in the longitudinal direction, and is formed of a material having heat resistance, insulation properties, and good thermal conductivity.

  The overcoat layer 28 is provided on the surface of the substrate 27 so as to cover the heating resistor 26, the electrode 29b, the conductive portion 29c, the electrode 30b, and the conductive portion 30c. The overcoat layer 28 is mainly intended to secure the electrical insulation between the heat generating resistor 26 and the surface of the heater 23 and the slidability between the surface of the heater 23 and the inner peripheral surface of the fixing film 22. It is provided. The overcoat layer 28 exemplifies a heat resistant glass layer having a thickness of 60 μm here. In FIG. 3, the overcoat layer 28 is omitted for the convenience of description.

  The feeding portion 29 a is provided on the surface of the substrate 27. The feed portion 29a exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  The electrode 29 b is provided on the surface of the substrate 27. The electrode 29 b is in contact with the entire region of the heating resistor 26 along the longitudinal direction of the substrate 27 at one end in the lateral direction of the substrate 27. The electrode 29b illustrates a screen pattern of silver palladium (Ag / Pd) here. Here, the short direction is the same as the conveyance direction of the recording material P.

  The conductive portion 29 c is provided on the surface of the substrate 27. The conductive portion 29c electrically connects the feeding portion 29a and the electrode 29b. The conductive portion 29 c exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  The feeding portion 30 a is provided on the surface of the substrate 27. The feeding part 30a exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  The electrode 30 b is provided on the surface of the substrate 27. The electrode 30 b is in contact with the entire region of the heating resistor 26 along the longitudinal direction of the substrate 27 at the other end in the lateral direction of the substrate 27. The electrode 30b exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  The conductive portion 30 c is provided on the surface of the substrate 27. The conductive portion 30 c electrically connects the feeding portion 30 a and the electrode 30 b. The conductive portion 30 c exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  The thermo switch 31 is provided on the back surface of the substrate 27 and is used as a safety device that shuts off the energization when the heater 23 abnormally heats up. The thermo switch 31 is configured by covering the bimetal with an aluminum cap member in contact with the back surface of the substrate 27, and the temperature of the heater 23 is transmitted to the bimetal via the cap member. When the thermal switch 31 reaches the critical temperature, the bimetal deforms and cuts off the current supply to the heater 23.

  The thermo switch 31 is provided at a position symmetrical to the thermistor 25 a with respect to the center of the heating resistor 26 in the longitudinal direction. Even when the voltage drop in the longitudinal direction of the heater 23 is taken into consideration, a temperature equivalent to the temperature detected by the thermistor 25 a is transmitted to the thermo switch 31. The thermo switch 31 is preferably provided so as to be symmetrical with the thermistor 25 a with respect to the longitudinal center of the heating resistor 26 so as to approach the center as much as possible. In addition, as a safety device which shuts off electricity supply at the time of abnormal temperature rise generation of the heater 23, it may replace with a thermo switch and a temperature fuse etc. may be used.

  The control unit 41 controls the temperature of the sheet passing area based on the detection result input from the thermistor 25a. The control unit 41 controls the temperature of the non-sheet passing area at the time of passing the recording material P of a small size by performing throughput control based on the detection result input from the thermistor 25 b. The control unit 41 performs throughput control because the temperature rise of the non-sheet passing area may occur when continuously passing the recording material P of extremely small size such as a postcard. The control unit 41 controls the temperature of the heater 23 based on the detection result of the current detector 44.

  Specifically, the control unit 41 performs control to turn on or off the triac 42 to control the power supplied to the heater 23 by phase control or frequency control or to turn on or off the switch 45. Switch control to perform temperature control.

  When the triac 42 is turned on by the control of the control unit 41, the AC power supply 43 energizes the feeding unit 129a via the thermo switch 31. When the triac 42 is turned off by the control of the control unit 41, the AC power supply 43 stops the energization of the power supply unit 129a through the thermo switch 31.

  The current detector 44 detects the current flowing through the heater 23 and outputs the detection result to the control unit 41.

  When the switch 45 is turned on by the control of the control unit 41, the switch 45 turns on the power supply unit 129 a from the AC power supply 43 via the thermo switch 31. When the switch 45 is turned off by the control of the control unit 41, the switch 45 stops the energization of the power supply unit 129 a from the AC power supply 43 via the thermo switch 31.

  The feeding portion 129 a is provided on the back surface of the substrate 27. The feeding portion 129a exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  As shown in FIG. 5, the conductive portion 129b is provided around the back surface of the substrate 27 and includes a rectangular wave-shaped pulse shaped portion 129d extended along the longitudinal direction. The conductive portion 129 b electrically connects the feeding portion 129 a and the feeding portion 129 c. The conductive portion 129 b exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  The feeding portion 129 c is provided on the back surface of the substrate 27. The feed portion 129 c exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  In the present embodiment, an overcoat layer can be provided as necessary to cover the conductive portion 129 b on the back surface of the substrate 27. This overcoat layer exemplifies a heat resistant glass layer having a thickness of 60 μm here.

  In the heater 23 having the above configuration, the length y (the length in the short direction of the installation area) of the portion including the heating resistor 26, the electrode 29b and the electrode 30b is in the short direction of the conductive portion 129b. The relationship is smaller than the overall length Y (y <Y). In the heater 23, the length x in the longitudinal direction of the heating resistor 26 (the length in the longitudinal direction of the installation area) is smaller than the entire length X in the longitudinal direction of the conductive portion 129b (x <X). Have. That is, the conductive portion 129 b is disposed on the back surface of the substrate 27 across the installation regions of the electrode 29 b and the electrode 30 b and the heating resistor 26.

<Operation of fixing device>
The operation of the fixing device 11 according to the first embodiment of the present invention will be described in detail.

  First, the drive roller (not shown) provided at the end of the cored bar 24 a of the pressure roller 24 is rotationally driven, whereby the pressure roller 24 rotates in the direction of the arrow B in FIG. 2.

  By the rotation of the pressure roller 24, a frictional force between the surface of the pressure roller 24 and the surface of the fixing film 22 at the fixing nip N exerts a rotational force on the fixing film 22, and the fixing film 22 is driven to rotate. At this time, while the fixing film 22 is in close contact with and slides on the surface of the heater 23, the fixing film 22 rotates in accordance with the rotational speed of the pressure roller 24 in the direction of arrow C in FIG. The heat of the heater 23 is transmitted to the recording material P of the fixing nip N via the fixing film 22.

  When the printing operation is started, the control unit 41 turns on the triac 42 to start energization of the heater 23. As a result, power is supplied from the AC power supply 43 to the power supply portion 129 a of the heater 23 through the thermo switch 31.

  Then, electricity is supplied from the feeding part 129a to the conducting part 129b, the feeding part 129c, the contact fitting not shown, the feeding part 29a, the conducting part 29c, the electrode 29b, the heating resistor 26, the electrode 30b, the conducting part 30c and the feeding part 30a in this order . As a result, the entire region of the heat generating resistor 26 generates heat and raises its temperature.

  The thermistor 25 a and the thermistor 25 b detect the temperature of the substrate 27 which is heated according to the temperature rise of the heating resistor 26. The control unit 41 A / D converts and takes in the detection result of the temperature output from the thermistor 25a and the thermistor 25b.

  The control unit 41 continues energization until the temperature detected by the thermistor 25a and the thermistor 25b reaches the target temperature. When the target temperature is reached, the control unit 41 controls the power supplied to the heater 23 by the TRIAC 42 by phase control or frequency control, based on the temperature detected by the thermistor 25a and the thermistor 25b. Perform temperature control.

  Specifically, when the temperature detected by the thermistor 25 a and the thermistor 25 b is lower than a predetermined set temperature, the control unit 41 turns on the triac 42 and the switch 45 to raise the temperature of the heater 23. When the temperature detected by the thermistor 25a and the thermistor 25b is equal to or higher than the set temperature, the control unit 41 turns off the triac 42 or the switch 45 to lower the temperature of the heater 23. Thus, the heater 23 is maintained at the set temperature.

  The fixing device 11 introduces the recording material P carrying an image into the fixing nip N in a state where the temperature of the heater 23 rises to the set temperature and the rotational peripheral speed of the fixing film 22 becomes steady. Then, the recording material P is nipped and conveyed together with the fixing film 22 at the fixing nip N in the short direction of the substrate 27, whereby the heat of the heater 23 is applied to the recording material P through the fixing film 22. Thus, the unfixed toner image t on the recording material P is heated and fixed to the recording material P.

  The recording material P conveyed from the fixing nip N is separated from the surface of the fixing film 22 and further conveyed.

  When the printing operation is completed, the control unit 41 turns off the triac 42 and terminates the energization of the heater 23.

<Operation of the heater when cracking occurs in the heater>
The operation of the heater 23 when the heater 23 according to the first embodiment of the present invention is cracked will be described in detail with reference to FIGS. 4 and 5.

  4 and 5, the crack D1 in FIG. 4 on the surface of the substrate 27 and the crack D1 'in FIG. 5 on the back surface of the substrate 27 show the same crack and are connected. Further, the crack D2 in FIG. 4 on the surface of the substrate 27 and the crack D2 'in FIG. 5 on the back surface of the substrate 27 show the same crack and are connected. Further, the crack E in FIG. 4 on the surface of the substrate 27 and the crack E ′ in FIG. 5 on the back surface of the substrate 27 show the same crack and are connected.

  Even when the crack D1 or the crack D2 shown in FIG. 5 which does not reach the conductive portion 29c or the conductive portion 30c is generated on the surface of the substrate 27, the crack D1 'or the crack D2' reaching the conductive portion 129b on the back surface of the substrate 27 To shut off the current path.

  In addition to the above, the heater 23 cuts off the current path by the conductive portion 129b even when a crack is generated from the middle of the feeding portion 30a to the electrode 29b without passing through the conductive portion 29c and the conductive portion 30c. be able to. In addition, even when a crack is generated up to the electrode 30b from the middle of the feeding portion 29a without passing through the conductive portion 29c and the electrode 29b, the conductive portion 129b can block the current path.

  In addition, even when a crack is generated up to the electrode 29b from the middle of the feeding portion 30a without passing through the conductive portion 30c and the electrode 30b, the conductive portion 129b can block the current path. Furthermore, even when the heater 23 has a crack that does not reach the conductive portion 29c and the conductive portion 30c, the conductive path can be blocked by the conductive portion 129b.

  As described above, in the present embodiment, the conductive portion 129 b is provided on the substrate 27 across the installation regions of the electrode 29 b and the electrode 30 b of the substrate 27 and the heating resistor 26. As a result, by adopting a configuration capable of reliably interrupting the current passage when cracking occurs, current can be reliably interrupted.

  Further, in the present embodiment, the thermo switch 31 is installed at a position symmetrical to the thermistor 25 a with respect to the center in the longitudinal direction of the heating resistor 26. Therefore, even when the voltage drop in the longitudinal direction of the heater 23 is taken into consideration, the temperature detected by the thermo switch 31 and the temperature detected by the thermistor 25 can be made equal. Thereby, accurate detection of the heater temperature becomes possible, and abnormal temperature rise of the heater 23 can be detected more accurately.

  Further, in the present embodiment, when the thermo switch 31 is disposed at a position symmetrical to the thermistor 25 a with respect to the center in the longitudinal direction of the heat generating resistor 26, the thermistor 25 a and the thermo switch 31 approach each other as much as possible. As a result, the temperature detected by the thermistor 25a is in the vicinity of the maximum temperature location in the longitudinal direction of the heater 23. Therefore, excessive temperature rise can be easily suppressed, abnormal temperature rise can be detected promptly, and safety can be enhanced. Can.

Second Embodiment
The configuration of the image forming apparatus according to the second embodiment of the present invention is the same as that shown in FIG. Further, the configuration of the fixing device according to the present embodiment is the same as that shown in FIG.

<Structure of heater>
The configuration of the heater 223 according to the second embodiment of the present invention will be described in detail with reference to FIGS. 7 and 8.

  In FIGS. 7 and 8, the same components as those in FIGS. 3 to 6 are denoted by the same reference numerals, and the description thereof will be omitted.

  The heater 223 as a heat generating member includes a thermistor 25a, a thermistor 25b, a heat generating resistor 26, a substrate 27, and an overcoat layer 28. In addition, the heater 223 includes a feeding unit 29a, an electrode 29b, a conducting unit 29c, a feeding unit 30a, an electrode 30b, a conducting unit 30c, a thermo switch 31, a control unit 41, and a triac 42. doing. Further, the heater 223 includes an AC power supply 43, a current detector 44, a switch 45, a power feeding unit 129a, a power feeding unit 129c, and a conductive unit 229b.

  The conductive portions 229 b are divided into two in the lateral direction on the back surface of the substrate 27 and routed, and are arranged in parallel along the lateral direction and extend along the longitudinal direction. And a plurality of pulse-shaped portions 229 d in the form of pulses. The conductive portion 229 b electrically connects the feeding portion 129 a and the feeding portion 129 c. The conductive portion 229 b exemplifies a screen pattern of silver palladium (Ag / Pd) here.

  In the heater 223 having the above configuration, the length y of the portion including the heating resistor 26, the electrode 29b, and the electrode 30b is smaller than the length Y in the lateral direction of the conductive portion 229b (y <Y) I have a relationship. In the heater 223, the length x in the longitudinal direction of the heat generating resistor 26 is smaller than the length X in the longitudinal direction of the conductive portion 229b (x <X). That is, the conductive portion 229 b is disposed on the back surface of the substrate 27 across the installation regions of the electrode 29 b and the electrode 30 b and the heating resistor 26.

<Operation of the heater when cracking occurs in the heater>
The operation of the heater 223 when the heater 223 according to the second embodiment of the present invention is cracked will be described in detail with reference to FIGS. 7 and 8.

  Even when the crack F shown in FIG. 7 which does not reach the conductive portion 29c or the conductive portion 30c is generated on the surface of the substrate 27, a crack F 'is generated on the back surface of the substrate 27 to reach the conductive portion 229b. It is cut off.

  In addition to the above, when the heater 223 produces a crack from the crack D1 shown in FIG. 4 to the crack D1 ′ shown in FIG. 5, and the crack D2 shown in FIG. 4 to the crack D2 ′ shown in FIG. Even in this case, the conductive path can be blocked by the conductive portion 229b.

  In addition, the heater 223 can block the current path by the conductive portion 229b even when a crack is generated from the middle of the feeding portion 30a to the electrode 29b without passing through the conductive portion 29c and the conductive portion 30c. . The heater 223 can cut off the current path by the conductive portion 229b even when a crack is generated from the middle of the feeding portion 29a to the electrode 30b without passing through the conductive portion 29c and the electrode 29b.

  Furthermore, the heater 223 can block the current path by the conductive portion 229b even when a crack is generated from the middle of the feeding portion 30a to the electrode 29b without passing through the conductive portion 30c and the electrode 30b. The heater 223 can cut off the current path by the conductive portion 229 b even when the heater does not reach the conductive portion 29 c and the conductive portion 30 c.

  The operation of the fixing device according to the present embodiment is the same as the operation of the fixing device according to the first embodiment, and thus the description thereof is omitted.

  As described above, according to the present embodiment, in addition to the effects of the first embodiment, the conductive portion 229b includes the plurality of pulse-shaped portions arranged in parallel along the short direction, thereby realizing the embodiment. As compared with the first aspect, when the crack is generated, the conduction path can be more surely shut off.

  In the present embodiment, two rows of pulse shaped portions are provided along the lateral direction, but three or more rows of pulse shaped portions may be provided along the lateral direction.

  The present invention is not limited to the above-described first embodiment and second embodiment, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

  Specifically, in the first embodiment and the second embodiment, the shape of the conductive portion provided on the back surface of substrate 27 is disposed across the installation region of electrode 29 b and electrode 30 b and heating resistor 26. The configuration is not limited to the pulse shape, and can be any shape. At this time, by finely dividing the drawing of the conductive portion on the back surface of the substrate 27 in the longitudinal direction and the short direction, the detection accuracy of the crack can be improved.

Reference Signs List 1 photosensitive drum 2 charging roller 3 laser beam scanner 4 developing unit 5 feeding cassette 6 feeding roller 7 registration roller 8a sheet pass 8b sheet pass 8c sheet pass 9 transfer roller 10 cleaning unit 11 fixing device 13 discharge port 14 discharge tray 21 stay Reference Signs List 22 fixing film 23 heater 24 pressure roller 24a metal core 24b elastic layer 24c mold release layer 25a thermistor 25b thermistor 26 heat generating resistor 27 substrate 28 overcoat layer 29a power feeding portion 29b electrode 29c conductive portion 30a power feeding portion 30b electrode 30c conductive portion Reference Signs List 31 thermo switch 41 control unit 42 triac 43 AC power supply 44 current detector 45 switch 100 image forming apparatus 129 a power supply unit 129 b conductive unit 129 c power supply unit 129 d pulse shape unit 223 heat 229b conductive portion 229d pulse shape portion

Claims (7)

An insulating substrate,
A heating resistor provided on one surface of the substrate;
An electrode provided on the heating resistor along the longitudinal direction of the substrate on one end side and the other end side of the substrate in the short direction;
A conductive portion disposed on the back surface of the one surface of the substrate and disposed across the installation region of the electrode and the heating resistor in the short side direction and the longitudinal direction, and connected to the electrode ,
A feed unit for supplying power to the electrode through the conductive unit;
A heat generating member characterized by having: The conductive portion is
The overall length in the lateral direction is made longer than the length in the lateral direction of the installation area, and the overall length in the longitudinal direction is longer than the longitudinal length of the installation area. Are disposed across the installation area,
The heat generating member according to claim 1, characterized in that The conductive portion is
A rectangular wave-shaped pulse shaped portion extended along the longitudinal direction on the back surface,
The heat generating member according to claim 1 or 2, characterized in that: The conductive portion is
A plurality of the pulse shape portions disposed in parallel along the short side direction,
The heat generating member according to claim 3, characterized in that: The installation area is
When the heating resistor provided on the one surface and the electrodes on the one end side and the other end side are projected on the back surface, the heating resistor projected on the back surface and the one end side and the other end side A region including the electrodes of
The heat generating member according to any one of claims 1 to 4, characterized in that: A heat generating member according to any one of claims 1 to 5;
Heating and rotating means including the heat generating member;
A pressing and rotating unit configured to nip and convey a recording material carrying an image at a fixing nip formed by pressing the heat generating member via the heating and rotating unit;
A fixing device characterized by having: A fixing device according to claim 6,
An image carrying means for carrying an image on a recording material;
Have
The fixing device is
Fixing the image on the recording material on which the image is carried by the image carrying means;
An image forming apparatus characterized by

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